Low cost antennas using conductive plastics or conductive composites

ABSTRACT

Low cost antennas formed of a conductive loaded resin-based material. The conductive loaded resin-based material comprises conductor fibers or conductor particles in a resin or plastic host wherein the ratio of the weight of the conductor fibers or conductor particles to the weight of the resin or plastic host is between about 0.20 and 0.40. The conductive fibers can be stainless steel, nickel, copper, silver, or the like. The antenna elements can be formed using methods such as injection molding or extrusion. Virtually any antenna fabricated by conventional means such as wire, strip-line, printed circuit boards, or the like can be fabricated using the conductive loaded resin-based materials. The conductive loaded resin-based material used to form the antenna elements can be in the form of a thin flexible woven fabric which can readily cut to the desired shape.

This patent application is a Continuation in Part of application Ser.No. 10/075,778, filed Feb. 14, 2002, which claimed priority to thefollowing U.S. Provisional Patent Applications:

-   -   Ser. No. 60/317,808, filed on Sep. 7, 2001.    -   Ser. No. 60/269,414, filed on Feb. 16, 2001, and    -   Ser. No. 60/317,808, filed on Feb. 15, 2001.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

This invention relates to antennas formed of conductive loadedresin-based materials comprising micron conductive powders or micronconductive fibers.

(2) Description of the Related Art

Antennas are an essential part of electronic communication systems thatcontain wireless links. Low cost antennas offer significant advantagesfor these systems.

U.S. Pat. No. 5,771,027 to Marks et al. describes a composite antennahaving a grid comprised of electrical conductors woven into the warp ofa resin reinforced cloth forming one layer of a multi-layer laminatestructure of an antenna.

U.S. Pat. No. 6,249,261 B1 to Solberg, Jr. et al. describes adirection-finding material constructed from polymer composite materialswhich are electrically conductive.

SUMMARY OF THE INVENTION

Antennas are essential in any electronic systems containing wirelesslinks. Such applications as communications and navigation requirereliable sensitive antennas. Antennas are typically fabricated frommetal antenna elements in a wide variety of configurations. Lowering thecost of antenna materials or production costs in fabrication of antennasoffers significant advantages for any applications utilizing antennas.

It is a principle objective of this invention to provide antennasfabricated from conductive loaded resin-based materials.

It is another principle objective of this invention to provide antennashaving two antenna elements fabricated from conductive loadedresin-based materials.

It is another principle objective of this invention to provide antennashaving an antenna element and a ground plane fabricated from conductiveloaded resin-based materials.

It is another principle objective of this invention to provide a methodof forming antennas from conductive loaded resin-based materials.

These objectives are achieved by fabricating the antenna elements andground planes from conductive loaded resin-based materials. Thesematerials are resins loaded with conductive materials to provide aresin-based material which is a conductor rather than an insulator. Theresins provide the structural material which, when loaded with micronconductive powders or micron conductive fibers, become composites whichare conductors rather than insulators.

Antenna elements are fabricated from the conductive loaded resins.Almost any type of antenna can be fabricated from the conductive loadedresin-based materials, such as dipole antennas, monopole antennas,planar antennas or the like. These antennas can be tuned to a desiredfrequency range.

The antennas can be molded or extruded to provide the desired shape. Theconductive loaded resin-based materials can be cut, injection molded,over-molded, laminated, extruded, milled or the like to provide thedesired antenna shape and size. The antenna characteristics depend onthe composition of the conductive loaded resin-based materials, whichcan be adjusted to aid in achieving the desired antenna characteristics.Virtually any antenna fabricated by conventional means such as wire,strip-line, printed circuit boards, or the like can be fabricated usingthe conductive loaded resin-based materials.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of a dipole antenna formed from aconductive loaded resin-based material.

FIG. 2A shows a front view of the dipole antenna of FIG. 1 showinginsulating material between the radiating antenna element and a groundplane.

FIG. 2B shows a front view of the dipole antenna of FIG. 1 showinginsulating material between both the radiating antenna element and thecounterpoise antenna element and a ground plane.

FIG. 2C shows an amplifier inserted between the radiating antennaelement and the coaxial cable center conductor for the dipole antenna ofFIG. 1.

FIG. 3 shows a segment of an antenna element formed from a conductiveloaded resin-based material showing a metal insert for connecting toconducting cable elements.

FIG. 4A shows a perspective view of a patch antenna comprising aradiating antenna element and a ground plane with the coaxial cableentering through the ground plane.

FIG. 4B shows a perspective view of a patch antenna comprising aradiating antenna element and a ground plane with the coaxial cableentering between the ground plane and the radiating antenna element.

FIG. 5 shows an amplifier inserted between the radiating antenna elementand the coaxial cable center conductor for the patch antenna of FIGS. 4Aand 4B.

FIG. 6 shows a perspective view of a monopole antenna formed from aconductive loaded resin-based material.

FIG. 7 shows a perspective view of a monopole antenna formed from aconductive loaded resin-based material with an amplifier between theradiating antenna element and the coaxial cable center conductor.

FIG. 8A shows a top view of an antenna having a single L shaped antennaelement formed from a conductive loaded resin-based material.

FIG. 8B shows a cross section view of the antenna element of FIG. 8Ataken along line 8B-8B′ of FIG. 8A.

FIG. 8C shows a cross section view of the antenna element of FIG. 8Ataken along line 8C-8C′ of FIG. 8A.

FIG. 9A shows a top view of an antenna formed from a conductive loadedresin-based material embedded in an automobile bumper.

FIG. 9B shows a front view of an antenna formed from a conductive loadedresin-based material embedded in an automobile bumper formed of aninsulator such as rubber.

FIG. 10A shows a schematic view of an antenna formed from a conductiveloaded resin-based material embedded in the molding of a vehicle window.

FIG. 10B shows a schematic view of an antenna formed from a conductiveloaded resin-based material embedded in the plastic case of a portableelectronic device.

FIG. 11 shows a cross section view of a conductive loaded resin-basedmaterial comprising a powder of conductor materials.

FIG. 12 shows a cross section view of a conductive loaded resin-basedmaterial comprising conductor fibers.

FIG. 13 shows a simplified schematic view of an apparatus for forminginjection molded antenna elements.

FIG. 14 shows a simplified schematic view of an apparatus for formingextruded antenna elements.

FIG. 15A shows a top view of fibers of conductive loaded resin-basedmaterial webbed into a conductive fabric.

FIG. 15B shows a top view of fibers of conductive loaded resin-basedmaterial woven into a conductive fabric.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following embodiments are examples of antennas fabricated usingconductive loaded resin-based materials. In some of the examples groundplanes are also used and these ground planes can be formed of eitherconductive loaded resin-based materials or metals. The use of theseconductive loaded resin-based materials in antenna fabricationsignificantly lowers the cost of materials and manufacturing processesused in the assembly antennas and the ease of forming these materialsinto the desired shapes. These materials can be used to form eitherreceiving or transmitting antennas. The antennas and/or ground planescan be formed using methods such as injection molding, overmolding, orextrusion of the conductive loaded resin-based materials.

The conductive loaded resin-based materials typically but notexclusively have a conductivity of between about 5 and 25 ohms persquare. The antenna elements, used to form the antennas, are formed ofthe conductive loaded resin-based materials and can be formed usingmethods such as injection molding, overmolding, or extrusion. Theantenna elements can also be stamped to produce the desired shape. Theconductive loaded resin-based material antenna elements can also cut ormilled as desired.

The conductive loaded resin-based materials comprise micron conductivepowders or fibers loaded in a structural resin. The micron conductivepowders are formed of metals such as nickel, copper, silver or the like.The micron conductive fibers can be nickel plated carbon fiber,stainless steel fiber, copper fiber, silver fiber, or the like. Thestructural material is a material such as a polymer resin. Structuralmaterial can be, here given as examples and not as an exhaustive list,polymer resins produced by GE PLASTICS, Pittsfield, Mass., a range ofother plastics produced by GE PLASTICS, Pittsfield, Mass., a range ofother plastics produced by other manufacturers, silicones produced by GESILICONES, Waterford, N.Y., or other flexible resin-based rubbercompounds produced by other manufacturers. The resin-based structuralmaterial loaded with micron conductive powders or fibers can be molded,using a method such as injection molding, overmolding, or extruded tothe desired shape. The conductive loaded resin-based materials can becut or milled as desired to form the desired shape of the antennaelements. The composition of the composite materials can affect theantenna characteristics and must be properly controlled. The compositecould also be in the family of polyesters with woven or webbed micronstainless steel fibers or other micron conductive fibers forming a clothlike material which, when properly designed in metal content and shape,can be used to realize a very high performance cloth antenna. Such acloth antenna could be embedded in a persons clothing as well as ininsulating materials such as rubber or plastic. The woven or webbedconductive cloths could also be laminated to materials such as Teflon,FR-4, or any resin-based hard material.

Refer now to FIGS. 1-10B for examples of antennas fabricated usingconductive loaded resin-based materials. These antennas can be eitherreceiving or transmitting antennas. FIG. 1 shows a perspective drawingof a dipole antenna with a radiating antenna element 12 and acounterpoise antenna element 10 formed from conductive loadedresin-based materials. The antenna comprises a radiating antenna element12 and a counterpoise antenna element 10 each having a length 24 and arectangular cross section perpendicular to the length 24. The length 24is greater than three multiplied by the square root of the crosssectional area. The center conductor 14 of a coaxial cable 50 iselectrically connected to the radiating antenna element 12 using a metalinsert 15 formed in the radiating antenna element 12. The shield 52 ofthe coaxial cable 50 is connected to the counterpoise antenna element 10using a metal insert formed in the counterpoise antenna element 10. Themetal insert in the counterpoise antenna element 10 is not visible inFIG. 1 but is the same as the metal insert 15 in the radiating antennaelement 12. The length 24 is a multiple of a quarter wavelength of theoptimum frequency of detection or transmission of the antenna. Theimpedance of the antenna at resonance should be very nearly equal to theimpedance of the coaxial cable 50 to assure maximum power transferbetween cable and antenna.

FIG. 3 shows a detailed view of a metal insert 15 formed in a segment 11of an antenna element. The metal insert can be copper or other metal. Ascrew 17 can be used in the metal insert 15 to aid in electricalconnections. Soldering or other electrical connection methods can alsobe used.

FIG. 1 shows an example of a dipole antenna with the radiating antennaelement 12 placed on a layer of insulating material 22, which is placedon a ground plane 20, and the counterpoise antenna element 10 placeddirectly on the ground plane 20. The ground plane 20 is optional and ifthe ground plane is not used the layer of insulating material 22 may notbe necessary. As another option the counterpoise antenna element 10 canalso be placed on a layer of insulating material 22, see FIG. 2A. If theground plane 20 is used it can also be formed of the conductive loadedresin-based materials.

FIG. 2A shows a front view of the dipole antenna of FIG. 1 for theexample of an antenna using a ground plane 20, a layer of insulatingmaterial 22 between the radiating antenna element 12 and the groundplane 20, and the counterpoise antenna element 10 placed directly on theground plane 20. FIG. 2B shows a front view of the dipole antenna ofFIG. 1 for the example of an antenna using a ground plane 20 and a layerof insulating material 22 between both the radiating antenna element 12and the counterpoise antenna element 10.

As shown in FIG. 2C, an amplifier 72 can be inserted between the centerconductor 14 of the coaxial cable and the radiating antenna element 12.A wire 70 connects metal insert 15 in the radiating antenna element 12to the amplifier 72. For receiving antennas the input of the amplifier72 is connected to the radiating antenna element 12 and the output ofthe amplifier 72 is connected to the center conductor 14 of the coaxialcable 50. For transmitting antennas the output of the amplifier 72 isconnected to the radiating antenna element 12 and the input of theamplifier 72 is connected to the center conductor 14 of the coaxialcable 50.

In one example of this antenna the length 24 is about 1.5 inches with asquare cross section of about 0.09 square inches. This antenna had acenter frequency of about 900 MHz.

FIGS. 4A and 4B show perspective views of a patch antenna with aradiating antenna element 40 and a ground plane 42 formed fromconductive loaded resin-based materials. The antenna comprises aradiating antenna element 40 and a ground plane 42 each having the shapeof a rectangular plate with a thickness 44 and a separation between theplates 46 provided by insulating standoffs 60. The square root of thearea of the rectangular square plate forming the radiating antennaelement 40 is greater than three multiplied by the thickness 44. In oneexample of this antenna wherein the rectangular plate is a square withsides of 1.4 inches and a thickness of 0.41 inches the patch antennaprovided good performance at Global Position System, GPS, frequencies ofabout 1.5 GHz.

FIG. 4A shows an example of the patch antenna where the coaxial cable 50enters through the ground plane 42. The coaxial cable shield 52 isconnected to the ground plane 42 by means of a metal insert 15 in theground plane. The coaxial cable center conductor 14 is connected to theradiating antenna element 40 by means of a metal insert 15 in theradiating antenna element 40. FIG. 4B shows an example of the patchantenna where the coaxial cable 50 enters between the radiating antennaelement 40 and the ground plane 42. The coaxial cable shield 52 isconnected to the ground plane 42 by means of a metal insert 15 in theground plane 42. The coaxial cable center conductor 14 is connected tothe radiating antenna element 40 by means of a metal insert 15 in theradiating antenna element 40.

As shown in FIG. 5 an amplifier 72 can be inserted between the coaxialcable center conductor 14 and the radiating antenna element 40. A wire70 connects the amplifier 72 to the metal insert 15 in the radiatingantenna element 40. For receiving antennas the input of the amplifier 72is connected to the radiating antenna element 40 and the output of theamplifier 72 is connected to the center conductor 14 of the coaxialcable 50. For transmitting antennas the output of the amplifier 72 isconnected to the radiating antenna element 40 and the input of theamplifier 72 is connected to the center conductor 14 of the coaxialcable 50.

FIG. 6 shows an example of a monopole antenna having a radiating antennaelement 64, having a height 71, arranged perpendicular to a ground plane68. The radiating antenna element 64 and the ground plane 68 are formedof conductive plastic or conductive composite materials. A layer ofinsulating material 66 separates the radiating antenna element 64 fromthe ground plane 68. The height 71 of the radiating antenna element 64is greater than three times the square root of the cross sectional areaof the radiating antenna element 64. An example of this antenna with aheight 71 of 1.17 inches performed well at GPS frequencies of about 1.5GHz.

FIG. 7 shows an example of the monopole antenna described above with anamplifier 72 inserted between the center conductor 14 of the coaxialcable 50 and the radiating antenna element 64. For receiving antennasthe input of the amplifier 72 is connected to the radiating antennaelement 64 and the output of the amplifier 72 is connected to the centerconductor 14 of the coaxial cable 50. For transmitting antennas theoutput of the amplifier 72 is connected to the radiating antenna element64 and the input of the amplifier 72 is connected to the centerconductor 14 of the coaxial cable 50.

FIGS. 8A, 8B, and 8C shows an example of an L shaped antenna having aradiating antenna element 80 over a ground plane 98. The radiatingantenna element 80 and the ground plane 98 are formed of conductiveloaded resin-based materials. A layer of insulating material 96separates the radiating antenna element 64 from the ground plane 98. Theradiating antenna element 80 is made up of a first leg 82 and a secondleg 84. FIG. 8A shows a top view of the antenna. FIG. 8B shows a crosssection of the first leg 82. FIG. 8C shows a cross section of the secondleg 84. FIGS. 8B and 8C show the ground plane 98 and the layer ofinsulating material 96. The cross sectional area of the first leg 82 andthe second leg 84 need not be the same. Antennas of this type may betypically built using overmolding technique to join the conductiveresin-based material to the insulating material.

Antennas of this type have a number of uses. FIGS. 9A and 9B show adipole antenna, formed of conductive loaded resin-based materials,embedded in an automobile bumper 100, formed of insulating material. Thedipole antenna has a radiating antenna element 102 and a counterpoiseantenna element 104. FIG. 9A shows the top view of the bumper 100 withthe embedded antenna. FIG. 9B shows the front view of the bumper 100with the embedded antenna.

The antennas of this invention, formed of conductive loaded resin-basedmaterials, can be used for a number of additional applications. Antennasof this type can be embedded in the molding of a window of a vehicle,such as an automobile or an airplane. FIG. 10A shows a schematic view ofsuch a window 106. The antenna 110 can be embedded in the molding 108.Antennas of this type can be embedded in the plastic housing, or be partof the plastic shell itself, of portable electronic devices such ascellular phones, personal computers, or the like. FIG. 10B shows aschematic view of a segment 112 of such a plastic housing with theantenna 110 embedded in the housing 112.

The conductive loaded resin-based material typically comprises a powderof conductor particles or a fiber of a conductor material in a resin orplastic host. FIG. 11 shows cross section view of an example ofconductor loaded resin-based material 212 having powder of conductorparticles 202 in a resin or plastic host 204. In this example thediameter 200 of the of the conductor particles 202 in the powder isbetween about 3 and 11 microns. FIG. 12 shows a cross section view of anexample of conductor loaded resin-based material 212 having conductorfibers 210 in a resin or plastic host 204. In this example the conductorfibers 210 have a diameter of between about 3 and 11 microns and alength of between about 5 and 10 millimeters. The conductors used forthese conductor particles 202 or conductor fibers 210 can stainlesssteel, nickel, copper, silver, or other suitable metals. These conductorparticles or fibers are embedded in a resin which in turn is embedded ina plastic host. As previously mentioned, the conductive loadedresin-based materials have a conductivity of between about 5 and 25 ohmsper square. To realize this conductivity the ratio of the weight of theconductor material, in this example the conductor particles 202 orconductor fibers 210, to the weight of the resin or plastic host 204 isbetween about 0.20 and 0.40.

Antenna elements formed from conductive loaded resin-based materials canbe formed in a number of different ways including injection molding orextrusion. FIG. 13 shows a simplified schematic diagram of an injectionmold showing a lower portion 230 and upper portion 231 of the mold.Uncured conductive loaded resin-based material is injected into the moldcavity 237 through an injection opening 235 and cured. The upper portion231 and lower portion 230 of the mold are then separated and the curedantenna element is removed.

FIG. 14 shows a simplified schematic diagram of an extruder for formingantenna elements using extrusion. Uncured conductive loaded resin-basedmaterial is placed in the cavity 239 of the extrusion unit 234. A piston236 or other means is then used to force the uncured conductive loadedresin-based material through an extrusion opening 240 which shapes thepartially cured conductive loaded resin-based material to the desiredshape. The conductive loaded resin-based material is then fully curedand is ready for use.

The conductive loaded resin based material can be formed into fiberswhich are woven or webbed into a conductive fabric. FIG. 15A shows awebbed conductive fabric 230. FIG. 15B shows a webbed conductive fabric232. This conductive fabric, 230 and/or 232, can be very thin and cutinto desired shapes to form antenna elements. These antenna elements cantake the shape of a host and attached as desired.

Antennas formed from the conductive loaded resin-based materials can bedesigned to work at frequencies from about 2 Kilohertz to about 300Gigahertz.

While the invention has been particularly shown and described withreference to the preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade without departing from the spirit and scope of the invention.

1. An antenna comprising: a number of antenna elements formed of aconductive loaded resin-based material, wherein said conductive loadedresin-based material comprises conductor fibers in a resin or plastichost and the ratio of the weight of said conductor fibers to the weightof said resin or plastic host is between about 0.20 and 0.40; andelectrical communication to and among said antenna elements.
 2. Theantenna of claim 1 further comprising a ground plane.
 3. The antenna ofclaim 2 wherein said ground plane is formed from said conductive loadedresin-based material.
 4. The antenna of claim 1 wherein said conductorfibers have a diameter of between about 3 and 11 microns.
 5. The antennaof claim 1 wherein said conductor fibers have a length of between 5 and7 millimeters.
 6. The antenna of claim 1 wherein said antenna elementsare imbedded in a plastic case for portable electronic equipment.
 7. Theantenna of claim 1 wherein said antenna elements are imbedded in vehiclewindow moldings.
 8. The antenna of claim 1 wherein the antennacomprising said number of antenna elements is designed for frequenciesbetween about 2 Kilohertz and 300 Gigahertz.
 9. The antenna of claim 1wherein the antenna comprising said number of antenna elements can be aradiating antenna or a receiving antenna.
 10. The antenna of claim 1wherein said conductor fibers are stainless steel, nickel, or copperfibers.
 11. An antenna comprising: a number of antenna elements formedof a conductive loaded resin-based material, wherein said conductiveloaded resin-based material comprises conductor particles in a resin orplastic host and the ratio of the weight of said conductor particles tothe weight of said resin or plastic host is between about 0.20 and 0.40;and electrical communication to and among said antenna elements.
 12. Theantenna of claim 11 further comprising a ground plane.
 13. The antennaof claim 12 wherein said ground plane is formed from said conductiveloaded resin-based material.
 14. The antenna of claim 11 wherein saidconductor particles have a diameter of between about 3 and 11 microns.15. The antenna of claim 11 wherein said conductor particles have aspherical shape.
 16. The antenna of claim 11 wherein said antennaelements are imbedded in a plastic case for portable electronicequipment.
 17. The antenna of claim 11 wherein said antenna elements areimbedded in vehicle window moldings.
 18. The antenna of claim 11 whereinthe antenna comprising said number of antenna elements is designed forfrequencies between about 2 Kilohertz and 300 Gigahertz.
 19. The antennaof claim 11 wherein the antenna comprising said number of antennaelements can be a radiating antenna or a receiving antenna.
 20. Theantenna of claim 11 wherein said conductor particles are stainlesssteel, nickel, or copper particles.
 21. A method of forming an antenna,comprising: providing a conductive loaded resin-based material whereinsaid conductive loaded resin-based material comprises conductor elementsin a resin or plastic host and the ratio of the weight of said conductorelements to the weight of said resin or plastic host is between about0.20 and 0.40; forming a number of antenna elements from said conductiveloaded resin-based material; and forming electrical connections to andamong said antenna elements.
 22. The method of claim 21 wherein saidantenna elements are formed using injection molding of said conductiveloaded resin-based material.
 23. The method of claim 21 wherein saidantenna elements are formed using extrusion of said conductive loadedresin-based material.
 24. The method of claim 21 wherein said antennaelements are formed from a flexible conductive fabric formed from saidconductive loaded resin-based material.
 25. The method of claim 21wherein said conductor elements are conductor fibers.
 26. The method ofclaim 25 wherein said conductor fibers have a diameter of between about3 and 11 microns and a length of between about 5 and 7 millimeters. 27.The method of claim 21 wherein said conductor elements are conductorparticles.
 28. The method of claim 27 wherein said conductor particleshave a diameter of between about 3 and 11 microns.
 29. The method ofclaim 21 wherein said conductor elements have a spherical shape and adiameter of between about 3 and 11 microns.
 30. The method of claim 21wherein said conductor elements are formed from stainless steel, nickel,or copper.